Powertrain, generic · Fuel and air metering (injector circuit)

P021F Cylinder 12 Injection Timing

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P021F reports a fault in the injection timing of cylinder 12 on a diesel engine. Unlike P01E1/P01E2 ('over retarded/advanced', the result of the injector learning routine in overrun), this code has no direction, and what it checks is up to the manufacturer. A cylinder 12 code only applies to engines with 12 or more cylinders. No manufacturer or vehicle using it was found – GM's documents stop at cylinder 8 (P021B), FCA's at cylinder 6, and Ford uses other codes. The description therefore follows the documented siblings: GM checks the injector's current rise electrically, FCA ties the code to injector learning. CARB requires diesel engines to detect injection that is too early or too late.

Likely causes

Injector of cylinder 12 faulty (coil, armature, wear, deposits)
Injector wiring or connector: contact resistance, corrosion, chafing
Engine software sets the code falsely (update available for some models)
Injector driver stage or boost voltage in the engine module
Wrong injector code, contaminated fuel or loose injector clamp

Symptoms

  • Check engine light on
  • Rough running or misfire, rough idle
  • Loss of power, smoke or knocking possible

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–1,200
Time0.5–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

fuel injector cylinder 12injector wiringengine control module

Related codes

P01E1P01E2P0212P232DP0312

References: law.cornell.edu, gsi.ext.gm.com.